The link you posted doesn't back up the statement that "No American used "delve" before ChatGPT 3.5". Instead it states that _few_ people used it in _biomedical papers_. I've seen it (and metaphors using the other words you noted) used in fiction for my entire life, and I sure as hell predate chatgpt. This is why it's a bad idea to consider every use of particular words to be AI generated. There are always some people who have larger vocabularies than others and use more words, including words some people have deemed giveaways of AI use.

That said, their use may raise suspicion of AI, but they are _not_ proof of AI. I don't want to live in a world where people with large vocabularies are not taken seriously. Such an anti-intellectual stance is extremely dangerous.

I bet the llm is biased towards the mtg card delver of secrets

But now Americans do use "delve" since 3.5. So what? No Americans used "cromulent" as a word either until Simpsons invented it. Is it not a real word? Does using it mean the Simpsons wrote it?